<!DOCTYPE html>
<html lang="en">

<head>
       
    <meta charset="UTF-8">
       
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
       
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
        <style>
        * {
            padding: 0;
            margin: 0;
        }

        .box {
            margin: 50px auto;
            width: 500px;
            height: 500px;
        }

        .topa {
            width: 250px;
            height: 250px;
            background-color: red;
            margin: 0 auto;
        }

        .lefta {
            float: left;
            width: 250px;
            height: 250px;
            background-color: orange;
        }

        .righta {
            float: right;
            width: 250px;
            height: 250px;
            background-color: green;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="topa">

        </div>
        <div class="lefta">

        </div>
        <div class="righta">

        </div>
    </div>
</body>

</html>